Controlling electric switches.



No- 827,353} PATENTED JULY 31, 1906.

i C. B. BVELBTH.

CONTROLLING ELECTRIC SWITCHES.

APPLICATION FILED OCT. 3. 1903.

3 SHEETS-SHEET 1.

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IHVEfiTQ Charles E.E\/e|eth.

No. 827,353. PATENTED JULY, a1, 1906.

'0. REVBLBTH. CONTROLLING ELECTRIC swmass.

APPLICATION IILBD 001. 3. 1903.

3 SHEBTBSHEET 2.

I l i No. 827,353. I v PATENTED JULY a1, 1906.

0. E. EYB'LE-TH. CONTROLLING ELBGTRIG SWITCHES.

APPLIOATION FILED OUT. a. 1903. I

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- UNITED sures PATENT curios.

CHARLES E. EVELETH, or SUHENEC"ADY, NEW YORK, ASSIGNOR To GENERALELECTRIC COMPANY, A CORPORATION or NEW YORK.

CCNTROLLING ELEGTRiC SWITCHES.

Specification of Letters Patent.

Patented July 81, 1906.

Anplication filed October 3, 1903, Serial No. 176.579.

1'0 mil whom it may concern..-

Be it known that I, CHARLES E. EVELETH, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Controlling ElectricSwitches, of which the following is a specification.

In distributing polyphase alternating electric currents it is now thepractice to employ series transformers in the several lines to operate'a trip-coil and open a main switch when a dangerous overload occurs,and in order to of overload it will not do so when a short circuitreduce cost only a sufficient number of such transformers is employed toassure an opening switch movement in case any line is overloaded. Thusin triphase systems two such transformers only need be employed, sinceif any of the three lines is overloaded one of the transformers willrespond. It has been found, however, that while such an arrange mentoperates reliably under most conditions occurs between the two lines inwhich the transformers are' interposed unless each transformer isprovided with a separate tripcircuit.

It is the object of my invention to provide a system in which a minimumnumber of trapisformers and a single trip-circuit maybe use My inventionconsists in so coordinating the phases, either in the transformersthemselves or in the circuit, that any change of phase relation under ashort circuit cannot operate to prevent a heavy current flowing in thetrip-circuit. Suppose, for example, a short circuit to occur between twolines of a triphase system in which are placed two series transformers.Evidently the energy of these two lines instead of passing to thedistributing-station will pass directly through the transformers. Theshort circuit destroys the phase difference on the lines and theelectromotive forces are no longer displaced one hundred and twentydegrees, but are one hundred and eighty degrees apart. In other words,when the short circuit occurs thetwo lines in which the transformers areconnected form a single-phase circuit, the current at an I assumedinstant passing out through one transformer and in through the other.Hence thetwo transformers will be pitted against each other or buck oneanother, and the voltage in the trip-circuit will be reduced to zero orto a low value, depending on the severity of the short circuit. Theswitch will therefore fail to trip and the safety apparatus beendangered. Now I have found by repeated tests that this possibility canbe avoided-by reversing the connections of the transformers withrelation to the trip-magnet, and this may be effected by relativelyreversing the primary windings or the secondary windings or differentsections of thetrip-coil The result of this system of connections isthat when the phase relations are destroyed by a Short circuit the twoelectromotive forces no longer oppose one another at'an angle of onehundred and eightyqo tem the currents in two lines have a phasedifference in normal operation of one hundred and twenty degrees; but byreason of my reverse system of connections the trip-circuit carries aresultant. not of two currents one hundred and twenty degrees apart, butof two currents sixty degrees apart, since the transformers arecross-connected, thus shifting one (phase one hundred and eighty degreesan bringing the two phases nearer together. This system ofconnectionsoperates with just as gre'at a degree of certainty formoderate overloads as those using independent trip-circuits; but in thecase of short circuits ithcts also with reliability, and there byaffords equal security at lessexpense of equipment.

"My invention may be applied to polyphase systems of any order, asquarter-phase, triing phase difference short-circuited to promote abetter action of the measuring instruments. Fig. '4 shows an applicationof my invention to a four-wire triphase system. Fig. 5 shows an'applica-.

' tion to a quarter-phase s stem where the two currents have indepen entcircuits. Fig.

6 shows a system similar to Fig. 5, having'an independent source oftrip-current. Fig. 7

- shows a'quarter-phase system in which the trip-coil is normallyshort-circuited, as in I v Fig. 3. Fig. 8 shows an equipment suitablefor an interconnectedquarter-phase system. Fig. 9 shows an equipmentsuitable for an interconnectedquarter-phase system having agrounded-neutral. Fig. 10 shows an apph cation to a triphase system inwhich the phases are magnetically interlinked on the core of thetrip-magnet; Fig. 11 shows the same arrangement as Fig. 10 in aquarterphase system. Fig. 12 shows an embod1- ment of the inventionwithout the use of current-transformers, and Fig. 13 shows an apout onone line and directly bao plication of the invention to a standard typeof oil-switch.

Referring first to Fig. 1 of the drawings, 1, 2, and 3 represent a.triphase circuit, and 4 and 5 series transformers. 6 is an oil-switch.adapted, when set, to be opened by the trip coil 7. With two seriestransformers obvi: ously under ordinary overload inany of the threemains the transformers would transfer to one or the other secondary aheavy current 'and the switch would be tripped; but if a short circuitoccurred between the. lines 1 and 3 at a point 8 between the generatingand distributingstations energy. would flow tethegenerator through theshort circuit. Thus-the normal phase difference between the coils 4.

' and 5 would be destro ed artially or wholly ma ly on.

in the ma and, as indicated by t e otted arrows, current would bereversed relatively in the two similarly related'to a commontrip-circuit the two opposing electromotive'forces would .ize eachother. I counteract this by nnecting-the wires 9 and 10. With ngement acommon trip-circuit -7 be used. The phases being nor- ;idred and twentydegrees apart cui't are now comblned in the tri -circu de rees apart,giving a resu tant current in t e tripcoil of approxiswitch is included.

ransformers. Thus if the secondaries were ma'tel 1.73 times that ofeither secondar 1 on the trip-coil, as will be hereinattershown.

' In-any case the phases must be relatively re versed and brou ht toaphasal relation in which under a s ort circuit a greater than normalcurrent Wlll flow on the. trrp-ccri= This system of connections hasother advanta es besides-renderin a sin is trio-circuit for all l nesavailable. Asmdicated above the phases are normally acting atsixtydegrees instead of one hundred and'twenty degrees, and thus less energy1s re 'uired of the transformers, permittin smal er transformers-tn beused, or if stan ard currenttranstormers are used'the readings of themeasuring iii-- struments used in the system have less error, due toless load on the transformers.

In Fig. 2 the ping energy is furnished by an auXi iarycircuit normallyopen at a point 11', and the transformers act on a relay 12 whenoverloaded to close theicircu it.

addition to the oil-switch 6, with its trip-coil 7, an ordinarytoggle-operated circuitbreaker' 6 is hereshown, having a trip-coil 7also operated by said relay 12. material what may be the type ofapparatus in the circuit governed by the current-trans-f formers so longas it acts only when excessive loads are carried by the transmission-zObviously it is im.

lines. The breaker 6-may control any desired circuit whichin theoperation of the;

. 10o switch is open-as, for example, the direct system it is desiredtoopen when the oil-' current circuit of a rotary transformer fed fromthe alternating-system in whichthe oilf It is customary.toincludein-thetrip cii cuit measuring instruments such .as amine-a ters andwattmeters. Where a number of meters are used,1t-1s oftenfound thatthe'tripcoil requires so much energy that an error is involved inithemeter indications. To avoidthis a relay'g of small energy capacity withits contacts normally short-circuitmg the tripcoil may be used. Thisarrangement is shown in Fig. 3, where 13 13" are ammete rs measuring thecurrent of the transformers and 12 the relay. Obviously the trip-coil-takes energy only when overload occurs, and thus the accuracy of themeasuring instruments is normally not disturbed.

In Fig. 4, representing a four-wire threephase tISLIISIIIlSSjOh. system,a current-trans-- phase or two-phase transmission system hav- 5 througha relay=1 2. Fig. 7 represents such a 'quarter-phase system withamme-ters 13 1.3

connected up with, each secondary of the transformers i and 5, thetrip-relay-12- normallysh ort-circ uitmg the trip-co1l 7, as in Fig. 3,to conduce to more accurate indications.

V Fig.' 8 shows an arrangement suitable for a quarter-phaseinterconnected transmissionlire. Three of the lines here includetransformers 4-, 4, and 5, the transformer licontrolling a "separaterelay 12, the other two having their connections crossed and controllingthe relay 12.

' InFig. 9 is represented a ounded quartor-phase system. Here it ecomesnecessary for reliable operationto insert atransformer for eachline,(designated 4 5 4' 5,) the two pairs 49 5*? and 4 5 beingcross-connected and each pair'contro'lling a trip device '7 through therelay 12 12*. A similar arare crossed, so'to speak, magneticallythat isto say, two magnetomotiveforces due tothe transformers have their phasesrelatively reversed. This may be effected b making two windings 15 15 ora split win ing and connecting with the secondaries of s. "thetransformers 4 and 5, so that the coils are reversely connected relativeto the corresponding transformer-poles. For exam le,

one poleof;one,transformer is connecte t0.

the lower end of one coil and a like pole of the other transformer isconnected to the upper end of the other coil, 'Thusthe magnetic fluxesare relatively shiftedlone hundred and eighty degrees, bringing thephases of mag netomotive force sixty degrees instead of one hundred andtwenty degrees apart. Thisarrangement provides an advantage over thosehereinbefore described in admitting of the use of three amineters' orwattmeters 13 13 13*. With the usual connection in a threephase circuitof two-current transformers it 1s customary to use three ammeters on atru nk-circuit from which various singlephase feeder-circuits aresupplied. The systemshown-inFig. 10 accomplishes the same thing with'asingle trip-circuit and two transformers. As clearly shown, the coils 1515? I are connected between the common junctionpoint and the poles ofthe transformer-secondaries, as previously indicated. The ammeters 13and 13? are in turn connected between the oppositepoles of thetransformer- 4 secondaries and a common junction-point 17', while thethird ammeter 13 is connected between the points lfiand 17. Thethirdammeter 13 will carry a phase one hundred and I twenty degreesdisplaced from each of the 16 of the relay-coils are connectedtogetherrangement would answer for a five-wire quarlines in a commoncircuit or two magnetomoothers. As will be evident upon carefulinspection, the instrument 13 carries a resultant of the currentsflowing through the other two, being included in a wire leading from thepoint 17 betweer. the other two instruments to the middle point 16 ofthe trip-relay coil. Thus the two currents are combined and have a valueequal to that in the third main. The'trip-coils are reversely connectedon the core and are therefore magnetically combined at sixty degrees.Fig. 11 represents a quarter-phase system in which the same combinationof magnetomotive force is effected in the trip-relay coils 15 15 themiddle point 16 of the trip-coil being connected to like terminals ofthe two, transformers 4 5 and thence to the ammeters 13 13". In thiscase the opposite poles of the transformer-secondaries and the middlepoint 5 at the point 18 and grounded, as indicated at 19. y Y

In Fig.712 the current from the lines enters the trip device directly.Two independent coils 15 15" are here employed on the trip 99 device,being reversely connected, as in the .case of thetransformer-secondaries-that is to say, the connections are such that ifthe coils are similarly wound, as illustrated, .phase aJ-enters at thetop of its coil 15 and phase I) at the bottom of its coil 15*.

In Fig. 13 a standard t e of oil-switch is shown provided with atripemagnet 15, having two independent trip-coils15 15", reverselyconnected relatively to two phases of a triphase transmission-line. Inthis con struction the moving contacts are carried by a yoke andverticallyreciprocated into and out of engagement with fixed contacts10- cated in the oil-can 21 by means of a connect- 1o 5 ing systemcomprising the bell-cranks 22 23 and the links-24 25. The outer end ofthe link 25, which extends through a suitable opening in the switchboard26,- is connected to the operatmg-levcr 27 by a pin-and-slot noconnection. A toggle 28 (shown in dotted lines and connected between thelink 25 and the lever 27 when'in the position illustrated) is slightlyoverset, so as to maintain a rigid connection between said lever andlink. The lever 27 is held in its closed position by a latch 29,- andthe moving solenoid-core by striking the center of the toggle 28 breaksit in case of an overload, and therefore frees the link 25 from itsrigid connection with the le- 12o ver 27 and allows the switch to openunder the action of gravity.

Thus it will be observed that I may combine either the electromotiveforces of two tive forces impressed by the lines on a common core, thetrip energy in all cases beingla resultant of relatively reversedphases, so that under a short circuit and, in fact, under all conditionsof overload a greater than normal 1 energy is'eXerted on the tripmechanism andthe switch opened reliably;

What T claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. In a polyphase alternating-current transmission system, a switch, atrip-circuit,

- and connections forbringing the phases closer togethenin thetrip-circuitto develop an abnormal flux in the trip-circuit under allOOH-r ditions of excessive'current in the lines. 2. In a transmissiontherefor, and

tem and thereby assuring opening of the switch under overload. I

3. 'In a .polyphase alternating current transmission system, a switch, atrip device therefor, and relatively reversed connections betweendifierent lines and the tripd'evice to maintain current in the latterwhen the linephases shift under short circuit. 4." A'polyphasealternating-current system provided with a switch, and a trip devicetherefor, two of the line phases being con nected in relatively reversedirections to magnetize said trip device.

35' y a trip-circuit common .to several phases, and

5. A polyphase' alternating-current system provided with a switch foropening the lines, a tr'ip'device therefor, two of the line-currentsacting in common on said trip device, and

connections fol-shifting their phases relatively one hundred and eightydegrees.

' 6. A polyphasealternating-current system provided with a switch foropening the lines,

polyphase alternating current system? a switch, a trip-circuitconnections for"relatively reversing aQp'lurality of phases in the tripsysthe lines,

connections combining said phases on the trip device with their phaseangle increased by one hundred and eighty degrees.

7. A polyphase alternating-current system providedwith aswitch foropening the lines, t 'o series transformers interposed therein, a commontrip-circuit supplied by said transformers,- and connections forshifting the phases relatively one hundred and eighty degrees. 1; 8.-,;-A triphase alternating-current system provided with a switch foropening the lines, two series transformers interposed in two of a commontrip-circuit supplied from the transformers, means for shifting thephase relation relatively one hundred and eighty degrees in thetrip-circuit, and a measuring instrument for each line connected withthe trip-circuit.

9. A triphase'alternating-current systein provided with a switch foropening the lines, two series transformersinterposed in two of thelines, a common trip system supplied from the.transf0rmer's,' means forshifting, the

